Question

Which one is acidic?

• A. \( \text{MnO} \)
• B. \( \text{Mn}_2\text{O}_3 \)
• C. \( \text{MnO}_2 \)
• D. \( \text{Mn}_2\text{O}_7 \)

Hint:

Oxides of metals with high oxidation states (such as Mn in +7) are usually acidic, while oxides of metals with lower oxidation states (like +2) are typically basic.

Answer 1

The Correct Option is D

To identify which oxide is acidic, it is important to look at the oxidation states of the central metal (manganese in this case) and the nature of the oxide.
\( \text{MnO} \): Here, manganese has an oxidation state of +2. Oxides of metals with lower oxidation states tend to be basic.
\( \text{Mn}_2\text{O}_3 \): In this oxide, manganese has an oxidation state of +3. This oxide is amphoteric, meaning it can act both as an acid and a base.
\( \text{MnO}_2 \): Here, manganese has an oxidation state of +4. This oxide is generally amphoteric but can also exhibit some acidic properties.
\( \text{Mn}_2\text{O}_7 \): In this oxide, manganese has an oxidation state of +7, which is quite high. Oxides with high oxidation states like +7 tend to be acidic, and \( \text{Mn}_2\text{O}_7 \) is indeed an acidic oxide.

Therefore, \( \text{Mn}_2\text{O}_7 \) (option D) is the acidic oxide, making it the correct answer.